Interview questions 1. What is the most important feature of Java? Java is a platform independent language. 2. What do you mean by platform independence? Platform independence means that we can write and compile the java code in one platform (eg Windows) and can execute the class in any other supported platform eg (Linux,Solaris,etc). 3. What is a JVM? JVM is Java Virtual Machine which is a run time environment for the compiled java class files. 4. Are JVM's platform independent? JVM's are not platform independent. JVM's are platform specific run time implementation provided by the vendor. 5. What is the difference between a JDK and a JVM? JDK is Java Development Kit which is for development purpose and it includes execution environment also. But JVM is purely a run time environment and hence you will not be able to compile your source files using a JVM. 6. What is a pointer and does Java support pointers? Pointer is a reference handle to a memory location. Improper handling of pointers leads to memory leaks and reliability issues hence Java doesn't support the usage of pointers. 1. What is the difference between a constructor and a method? A constructor is a member function of a class that is used to create objects of that class. It has the same name as the class itself, has no return type, and is invoked using the new operator. A method is an ordinary member function of a class. It has its own name, a return type (which may be void), and is invoked using the dot operator. 2. What is the purpose of garbage collection in Java, and when is it used? The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused.
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Interview questions
1. What is the most important feature of Java?
Java is a platform independent language.
2. What do you mean by platform independence?
Platform independence means that we can write and compile the java code in one platform (eg Windows) and can execute the class in any other supported platform eg (Linux,Solaris,etc).
3. What is a JVM?
JVM is Java Virtual Machine which is a run time environment for the compiled java class files.
4. Are JVM's platform independent?
JVM's are not platform independent. JVM's are platform specific run time implementation provided by the vendor.
5. What is the difference between a JDK and a JVM?
JDK is Java Development Kit which is for development purpose and it includes execution environment also. But JVM is purely a run time environment and hence you will not be able to compile your source files using a JVM.
6. What is a pointer and does Java support pointers?
Pointer is a reference handle to a memory location. Improper handling of pointers leads to memory leaks and reliability issues hence Java doesn't support the usage of pointers.
1. What is the difference between a constructor and a method?
A constructor is a member function of a class that is used to create objects of that class. It has the same name as the class itself, has no return type, and is invoked using the new operator.
A method is an ordinary member function of a class. It has its own name, a return type (which may be void), and is invoked using the dot operator.
2. What is the purpose of garbage collection in Java, and when is it used?
The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused.
A Java object is subject to garbage collection when it becomes unreachable to the program in which it is used.
3. Describe synchronization in respect to multithreading.
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources.
Without synchonization, it is possible for one thread to modify a shared variable while another thread is in the process of using or updating same shared variable. This usually leads to significant errors.
4. What is an abstract class?
Abstract class must be extended/subclassed (to be useful). It serves as a template. A class that is abstract may not be instantiated (ie. you may not call its constructor), abstract class may contain static data.
Any class with an abstract method is automatically abstract itself, and must be declared as such. A class may be declared abstract even if it has no abstract methods. This prevents it from being instantiated.
5. What is the difference between an Interface and an Abstract class?
An abstract class can have instance methods that implement a default behavior. An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract.
An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract
methods.
6. Explain different way of using thread?
The thread could be implemented by using runnable interface or by inheriting from the Thread class.
The former is more advantageous, 'cause when you are going for multiple inheritance, the only interface can help.
DBMS
1. What is database?
A database is a logically coherent collection of data with some inherent meaning, representing some aspect of real world and which is designed, built and populated with data for a specific purpose.
2. What is DBMS?
It is a collection of programs that enables user to create and maintain a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various applications.
3. What is a Database system?
The database and DBMS software together is called as Database system.
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1. Redundancy is controlled.2. Unauthorised access is restricted.3. Providing multiple user interfaces.4. Enforcing integrity constraints.5. Providing backup and recovery.
5. What are the disadvantage in File Processing System?
1. Data redundancy and inconsistency.2. Difficult in accessing data.3. Data isolation.4. Data integrity.5. Concurrent access is not possible.6. Security Problems.
6. Describe the three levels of data abstraction?
The are three levels of abstraction:
1. Physical level: The lowest level of abstraction describes how data are stored.2. Logical level: The next higher level of abstraction, describes what data are stored in
database and what relationship among those data.3. View level: The highest level of abstraction describes only part of entire database.
PHP
What is PHP?
PHP: Hypertext Preprocessor is open source server-side scripting language that is widely used for web development. PHP scripts are executed on the server. PHP allows writing dynamically generated web pages efficiently and quickly. The syntax is mostly borrowed from C, Java and perl. PHP is free to download and use.
What is PEAR in php?
PEAR(PHP Extension and Application Repository) is a framework and repository for reusable PHP components. PEAR is a code repository containing all kinds of php code snippets and libraries.
PEAR also offers a command-line interface that can be used to automatically install "packages".
Explain how to submit form without a submit button.
We can achieve the above task by using JavaScript code linked to an event trigger of any form field and call the document.form.submit() function in JavaScript code.
Echo vs. print statement.
echo() and print() are language constructs in PHP, both are used to output strings. The speed of both statements is almost the same.
echo() can take multiple expressions whereas print cannot take multiple expressions.
Print return true or false based on success or failure whereas echo doesn't return true or false.
$message vs. $$message in PHP.
$message is a variable with a fixed name. $$message is a variable whose name is stored in $message.
If $message contains "var", $$message is the same as $var.
Explain the different types of errors in PHP.
Notices, Warnings and Fatal errors are the types of errors in PHP
Notices:
Notices represents non-critical errors, i.e. accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all but whenever required, you can change this default behavior.
Warnings:
Warnings are more serious errors but they do not result in script termination. i.e calling include() a file which does not exist. By default, these errors are displayed to the user.
Fatal errors:
Fatal errors are critical errors i.e. calling a non-existent function or class. These errors cause the immediate termination of the script.
Explain the importance of the function htmlentities.
The htmlentities() function converts characters to HTML entities.
What is MIME?
MIME - Multi-purpose Internet Mail Extensions.
MIME types represents a standard way of classifying file types over Internet.
Web servers and browsers have a list of MIME types, which facilitates files transfer of the same type in the same way, irrespective of operating system they are working in.
A MIME type has two parts: a type and a subtype. They are separated by a slash (/).
MIME type for Microsoft Word files is application and the subtype is msword, i.e. application/msword.
PHP basic questions:1) What is PHP?
PHP is a web language based on scripts that allows developers to dynamically create
generated web pages.
2) What does the initials of PHP stand for?
PHP means PHP: Hypertext Preprocessor.
3) Which programming language does PHP resemble to?
PHP syntax resembles Perl and C
4) What does PEAR stands for?
PEAR means “PHP Extension and Application Repository”. it extends PHP and provides a
higher level of programming for web developers.
5) What is the actually used PHP version?
Version 5 is the actually used version of PHP.
6) How do you execute a PHP script from the command line?
Just use the PHP command line interface (CLI) and specify the file name of the script to be
executed as follows:
PHP
1 php script.php
7) How to run the interactive PHP shell from the command line
interface?
Just use the PHP CLI program with the option -a as follows:
PHP
1 php -a
8) What are the correct and the most two common way to start and
finish a PHP block of code?
The two most common ways to start and finish a PHP script are: <?php [ — PHP code—-
] ?> and <? [— PHP code —] ?>
9) How can we display the output directly to the browser?
To be able to display the output directly to the browser, we have to use the special tags <?=
and ?>.
10) What is the main difference between PHP 4 and PHP 5?
PHP 5 presents many additional OOP (Object Oriented Programming) features.
11) Is multiple inheritance supported in PHP?
PHP includes only single inheritance, it means that a class can be extended from only one
single class using the keyword ‘extended’.
12) What is the meaning of a final class and a final method?
‘final’ is introduced in PHP5. Final class means that this class cannot be extended and a
final method cannot be overrided.
13) How comparison of objects is done in PHP5?
We use the operator ‘==’ to test is two object are instanced from the same class and have
same attributes and equal values. We can test if two object are refering to the same
instance of the same class by the use of the identity operator ‘===’.
14) How can PHP and HTML interact?
It is possible to generate HTML through PHP scripts, and it is possible to pass informations
from HTML to PHP.
15) What type of operation is needed when passing values through a
form or an URL?
If we would like to pass values througn a form or an URL then we need to encode and to
decode them using htmlspecialchars() and urlencode().
16) How can PHP and Javascript interact?
PHP and Javascript cannot directly interacts since PHP is a server side language and
Javascript is a client side language. However we can exchange variables since PHP is able
to generate Javascript code to be executed by the browser and it is possible to pass
specific variables back to PHP via the URL.
17) What is needed to be able to use image function?
GD library is needed to be able execute image functions.
18) What is the use of the function ‘imagetypes()’?
imagetypes() gives the image format and types supported by the current version of GD-
PHP.
19) What are the functions to be used to get the image’s properties
(size, width and height)?
The functions are getimagesize() for size, imagesx() for width and imagesy() for height.
20) How failures in execution are handled with include() and require()
functions?
If the function require() cannot access to the file then it ends with a fatal error. However, the
include() function gives a warning and the PHP script continues to execute.
21) What is the main difference between require() and require_once()?
require() and require_once() perform the same task except that the second function checks
if the PHP script is already included or not before executing it.
92) What is the difference between ereg_replace() and eregi_replace()?
The function eregi_replace() is identical to the function ereg_replace() except that it ignores
case distinction when matching alphabetic characters.
93) Is it possible to protect special characters in a query string?
Yes, we use the urlencode() function to be able to protect special characters.
94) What are the three classes of errors that can occur in PHP?
The three basic classes of errors are notices (non-critical), warnings (serious errors) and
fatal errors (critical errors).
95) What is the difference between characters \034 and \x34?
\034 is octal 34 and \x34 is hex 34.
96) How can we pass the variable through the navigation between the
pages?
It is possible to pass the variables between the PHP pages using sessions, cookies or
hidden form fields.
97) Is it possible to extend the execution time of a php script?
The use of the set_time_limit(int seconds) enables us to extend the execution time of a php
script. The default limit is 30 seconds.
98) Is it possible to destroy a cookie?
Yes, it is possible by setting the cookie with a past expiration time.
99) What is the default session time in php?
The default session time in php is until closing of browser
100) Is it possible to use COM component in PHP?
Yes, it’s possible to integrate (Distributed) Component Object Model components ((D)COM)
in PHP scripts which is provided as a framework.
Once again: Brush up PHP
1. What is PHP?
PHP stands for PHP : Hypertext Preprocessor.
PHP is a server side scripting language, like ASP
PHP scripts are executed on the server.
PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL,
Generic ODBC, etc.)
PHP is an open source software (OSS).
PHP is free to download and use
2.What is the basic syntax of Php?
<?p<?php
?>
A PHP scripting block can be placed anywhere in the document.
3. What is the difference between static and Dynamic Web Sites?
The Web sites were made up of a collection of documents written in the HTML
language. The pages were text based, simple, and static. Every time the user reloaded
a page in his or her browser, it looked exactly the same. It consisted of HTML text,
images, and links.
A dynamic Web site is one with content that is regenerated every time a user visits or
reloads the site. Although it can be as simple as displaying the current date and time, in
most cases it requires the use of a database, which contains the site’s information, and
a scripting language that can retrieve the information from the database. Google and
Yahoo! are examples of dynamic sites, search engines that create customized pages
based on a key word or phrase you type.
4. What is the name of the scripting engine that powers PHP?
PHP is a scripting engine called the Zend Engine 2.
5. What is the difference between PHP4 and PHP5?
PHP4 cannot support oops concepts and Zend engine 1 is used.
PHP5 supports oops concepts and Zend engine 2 is used. Error supporting is increased
in PHP5. XML and SQLLite will is increased in PHP5
6. What is an Array in PHP?
An array in PHP is really an ordered map of pairs of keys and values.
7. What are the advantages of MySQL and PHP?
PHP, a simple and powerful scripting language, and MySQL, a solid and reliable
database server, make a perfect marriage between two modern technologies for
building databasedriven, dynamic Web sites. Some of the advantages of both PHP and
MySQL are :
High performance
Built in libraries
Extensibility
Relatively low cost
Portability
Developer community
Ease of learning
8. What is PHP’s configuration file called?
PHP’s configuration file is called php.ini.
9. Which function would you use to merge two arrays?
You can merge arrays with the array_merge() function.
10. What is a session?
A session is a logical object created by the PHP engine to allow you to preserve data
across subsequent HTTP requests.
11. Name a new feature introduced with PHP 5?
PHP 5 introduces (among other things) SQLite support, improved XML support, and a
significantly improved object model.
12. What is a persistent cookie?
A persistent cookie is a cookie which is stored in a cookie file permanently on the
browser's computer. By default, cookies are created as temporary cookies which stored
only in the browser's memory. When the browser is closed, temporary cookies will be
erased.
13. What is the difference between temporary cookies and persistent cookies?
Temporary cookies can not be used for tracking long term information.
Persistent cookies can be used for tracking long term information.
Temporary cookies are safer because no programs other than the browser can access
them.
Persistent cookies are less secure because users can open cookie files see the cookie
values..
14. What is a cookie?
A cookie is a small amount of information sent by a Web server to a web browser and
then sent back unchanged by the browser each time it accesses that server. HTTP
cookies are used for authenticating, tracking, and maintaining specific information
about users, such as site preferences and the contents of their electronic shopping
carts
15. What is Session Id?
A session ID is an identification string of a session. Since there might be multiple
visitors coming to your Web site at the same time, the PHP engine needs to maintain
multiple sessions concurrently. Session IDs are created and maintained by the PHP
engine to identify sessions.
Extra PHP questions:
1. What is PHP?
PHP is a server side scripting language commonly used for web applications. PHP has many frameworks and cms for creating websites.Even a non technical person can cretae sites using its CMS.WordPress,osCommerce are the famus CMS of php.It is also an object oriented programming language like java,C-sharp etc.It is very eazy for learning
2. What is the use of "echo" in php?
It is used to print a data in the webpage, Example: <?php echo 'Car insurance'; ?> , The following code print the text in the webpage
3. How to include a file to a php page?
We can include a file using "include() " or "require()" function with file path as its parameter.
4. What's the difference between include and require?
If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
5. require_once(), require(), include().What is difference between them?
require() includes and evaluates a specific file, while require_once() does that only if it has not been included before (on the same page). So, require_once() is recommended to use when you want to include a file where you have a lot of functions for example. This way you make sure you don't include the file more times and you will not get the "function re-declared" error.
6. Differences between GET and POST methods ?
We can send 1024 bytes using GET method but POST method can transfer large amount of data and POST is the secure method than GET method .
7. How to declare an array in php?
Eg : var $arr = array('apple', 'grape', 'lemon');
8. What is the use of 'print' in php?
This is not actually a real function, It is a language construct. So you can use with out parentheses with its argument list.Example print('PHP Interview questions'); print 'Job Interview ');
9. What is use of in_array() function in php ?
in_array used to checks if a value exists in an array
10. What is use of count() function in php ?
count() is used to count all elements in an array, or something in an object
11. What’s the difference between include and require?
It’s how they handle failures. If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
12. What is the difference between Session and Cookie?
The main difference between sessions and cookies is that sessions are stored on the server, and cookies are stored on the user’s computers in the text file format. Cookies can not hold multiple variables,But Session can hold multiple variables.We can set expiry for a cookie,The session only remains active as long as the browser is open.Users do not have access to the data you stored in Session,Since it is stored in the server.Session is mainly used for login/logout purpose while cookies using for user activity tracking
13. How to set cookies in PHP?
Setcookie("sample", "ram", time()+3600);
14. How to Retrieve a Cookie Value?
eg : echo $_COOKIE["user"];
15. How to create a session? How to set a value in session ? How to Remove data from a session?
Create session : session_start();Set value into session : $_SESSION['USER_ID']=1;Remove data from a session : unset($_SESSION['USER_ID'];
16. what types of loops exist in php?
for,while,do while and foreach (NB: You should learn its usage)
17. How to create a mysql connection?
mysql_connect(servername,username,password);
18. How to select a database?
mysql_select_db($db_name);
19. How to execute an sql query? How to fetch its result ?
$my_qry = mysql_query("SELECT * FROM `users` WHERE `u_id`='1'; "); $result = mysql_fetch_array($my_qry);echo $result['First_name'];
20. Write a program using while loop
$my_qry = mysql_query("SELECT * FROM `users` WHERE `u_id`='1'; "); while($result = mysql_fetch_array($my_qry)){echo $result['First_name'.]."<br/>";}
21. How we can retrieve the data in the result set of MySQL using PHP?
o 1. mysql_fetch_rowo 2. mysql_fetch_arrayo 3. mysql_fetch_objecto 4. mysql_fetch_assoc
22. What is the use of explode() function ?
Syntax : array explode ( string $delimiter , string $string [, int $limit ] ); This function breaks a string into an array. Each of the array elements is a substring of string formed by splitting it on boundaries formed by the string delimiter.
23. What is the difference between explode() and split() functions?
Split function splits string into array by regular expression. Explode splits a string into array by string.